Tour Tech: Rotor Flow aero crankset

The extra bolt hole allows for an extra five steps of adjustment for Rotor's Q-Rings. Note the lines on the spider marked "OCP," noting the regular bolt circle, and "OCP +1/2," noting the half step. Photo: Caley Fretz | VeloNews.com

LIÈGE, Belgium (VN) — The search for free seconds never ceases as riders prepare to tackle the 100km of contre le montre in this year’s Tour de France. With an eye towards the fine details, Garmin-Sharp-Barracuda crank sponsor Rotor released a brand-new aero crankset Thursday morning.

The cranks, dubbed Flow, will be present on all of Garmin’s time-trial bikes and were designed using computation fluid dynamics (CFD), a common theme in the latest generation of aero gear to hit the market. Development was performed in conjunction with Garmin’s director of sport science, Robby Ketchell, who was used as an aero consultant within both the CFD work and in the wind tunnel.

Crank aerodynamics is particularly tricky, Rotor says, due to the influence of the rider’s feet and legs and, of course, because the cranks rotate. The company took a close look at how to best smooth airflow given all the inherent turbulence in the crank area.

A solid spider is a given, and the Flow version appears similar to the one already available for Rotor’s 3D crank arms. But a closer look shows that this new spider offers up a new second bolt hole, doubling the mount points available for Rotor’s ovalized Q-Rings from five to 10.

Rotor calls the new mount the Micro Adjust Spider, and its placement allows for a adjustment of the Q-rings in half-step increments. The feature is one Rotor’s pro riders requested, according to Rotor research specialist Christie O’Hara.

The arms themselves are heavily shaped to provide optimal airflow. They are narrower near the axle and spread wide near the pedal. Both edges sharpen as they move towards the pedals as well.

Rotor says the cranks will save 26 seconds over 180km at 200 watts, or a relatively average power output over the Ironman bike distance.

Why not run the cranks all the time? “It’s a bit of extra weight, and it’s rotating weight,” said Ketchell.

Weight of the cranks without rings is a competitive 562 grams, with 175mm arms, and availability is slated for September.